Method for ascertaining the content of oxygen in fused steel



United States Patent 3,252,760 METHOD FOR ASCERTAINING THE CONTENT OF OXYGEN IN FUSE!) STEEL Otto Winkler, Balzers, and Thaddiius Kraus, Vaduz, Liechtenstein, assignors to Bendix Balzers Vacuum Inc, Rochester, N.Y.

No Drawing. Filed Apr. 4, 1963, Ser. No. 269,401

3 Claims. (Cl. 23---23tl) The present invention relates to a method for ascertaining the content of oxygen in fused steel.

The quick and reliable ascertaining of the content of oxygen in fused steel is of great importance in the practice of steel making. Since the usual method for ascertaining the content of oxygen, in which a sample is fused in a graphite crucible and the oxygen given off in the form of carbon monoxide is measured, takes an average of at least 5-30 minutes per analysis, the contemporaneous control of steel production during the melting operation has not yet been possible.

The great difiiculty in the analysis of liquid steel samples is that gas evolves from the sample in an uncontrollable manner prior to the solidification of the sample causing the gas content to vary during the analysis which could lead to erroneous results. It is known to prevent this premature giving off of gases by adding a certain quantity of aluminum to the liquid sample; this so-called killing of the melt, however, causes the oxygen to be bound more firmly and, as experience has shown, to result in the oxygen being given off very slowly and appearing in the subsequent analysis in the form of carbon monoxide as a result of reaction with carbon in the crucible. Accordingly it was considered necessary to use very high temperatures of more than 1800 C. when de-gassing such killed melts in an extraction furnace in order to liberate the gases as completely as possible. Nevertheless analyses of this kind made at very high temperatures require five to thirty minutes for completion. Investigations by the inventor have proved that the results have still been very inaccurate. Since no quantitative giving off of gases by the aluminumkilled steel samples could be attained, the errors in ascertaining the oxygen content amounted often up to 50%.

The invention has the object of overcoming these difiiculties and of providing a method for quickly and reliably ascertaining the content of oxygen in fused steel samples.

With these and other objects in view which will become apparent later from this specification we provide a method for ascertaining the content of oxygen in fused steel, comprising the steps of killing a fused sample of said steel with aluminum, allowing said sample to solidify, preparing a melt containing a metal of the group consisting of nickel and cobalt in a graphite crucible, introducing said solidified sample into said melt so as to fuse therein and to develop gases containing carbon monoxide, and performing a hot extraction analysis of the gases developing. The quantity of carbon monoxide forming can be measured in the usual way and serve as a measure of the content of oxygen. When proceeding according to the invention, surprisingly the quantitative giving off of gases is terminated in a few seconds after inserting the sample.

The use of prepared melt of any metal for facilitating the fusing of a solid sample thrown into it, is known in itself; the effect of the present invention is, however, not based on the quick fusing of the solid sample which could be carried out with prepared melts consisting of many different auxiliary metals, but-as tests have proved-is based on quite a specific effect which apparently occurs only in the special case of ascertaining the oxygen content of aluminum- .illed steel samples, and only in conjunction with a prepared melt containing nickel or cobalt. Prepared melts of pure iron which, for example, would likewise be capable of speeding up the fusing of the sample, do not shorten the analysis period. Likewise no other prepared melts not containing nickel or cobalt have been found which have the aforesaid effect.

For carrying out the invention, prepared melts may be used which contain nickel or cobalt as an alloy. It is, however, the simplest way to use a prepared melt of pure nickel or cobalt.

For example, a vacuum hot extraction analysis can be carried out in the usual manner with the only difference that according to the invention before introducing the sample, for example, a piece of commercially available pure nickel is thrown into a crucible, pre-melted there and if necessary preliminarily de-gassed, and thereafter the sample proper is inserted and the ascertaining of oxygen by measuring the carbon monoxide given off is carried out in the usual manner.

While we have herein described what may be considered a typical and particularly useful embodiment of our said invention, we Wish it to be understood that we do not limit ourselves to the details of the method described herein above, for obvious modifications will occur to a person skilled in the art.

What we claim as our invention and desire to secure by Letters Patent is:

1. A method for ascertaining the content of oxygen in fused steel, comprising the steps of killing a fused sample of said steel with aluminum, causing said sample to solidify, preparing a melt containing a metal of the group consisting of nickel and cobalt in a graphite crucible, introducing said solidified sample into said melt so as to fuse therein and to develop gases containing carbon monoxide, and performing a hot extraction analysis of the gases developing.

2. A method as claimed in claim 1, wherein said prepared melt consists of pure cobalt.

3. A method as claimed in claim 1, wherein said prepared melt consists of pure nickel.

References Cited by the Examiner UNITED STATES PATENTS 2,336,075 12/1943 Derge. 3,062,624 11/1962 Peifer.

MORRIS O. WOLK, Primary Examiner.

JAMES H. TAYMAN, Examiner.

D. S. LILLY, Z. PAROCZAY, Assistant Examiners. 

1. A METHOD FOR ASCERTAINING THE CONTENT OF OXYGEN IN FUSED STEEL, COMPRISING THE STEPS OF KILLING A FUSED SAMPLE OF SAID STEEL WITH ALUMINUM, CAUSING SAID SAMPLE TO SOLIDIFY, PREPARING A MELT CONTAINING A METAL OF THE GROUP CONSISTING OF NICKEL AND COBALT IN A GRAPHITE CRUCIBLE, INTRODUCING SAID SOLIDIFIED SAMPLE INTO SAID MELT SO AS TO FUSE THEREIN AND TO DEVELOP GASES CONTAINING CARBON MONOXIDE, AND PERFORMING A HOT EXTRACTION ANALYSIS OF THE GASES DEVELOPING. 